National Geographic News
Scientists have shown that, for hepetitis B vaccine, genetically modified potatoes may be an alternative to the syringe and needle.
The hepatitis B virus (HBV) causes liver failure and liver cancer. Despite the availability of a safe, injectable vaccine, the virus currently infects an estimated 350 million people worldwide and kills about a million people every year.
In recent years scientists have raced to develop oral vaccines with genetically modified plants as a means to overcome the economic and safety limitations of syringe-and-needle vaccination programs, especially in developing countries.
"The whole concept of oral vaccines, versus injections, is a very attractive one. As you can imagine, we are used to taking things by mouth. They are easy, and there are not associated problems with potential contamination due to syringes and needles," said Yasmin Thanavala, an immunologist at the Roswell Park Cancer Institute in Buffalo, New York.
Previously researchers have shown that potatoes can deliver vaccines for intestinal pathogens such as the E. coli and Norwalk viruses, which enter the body via the mouth.
This week in the research journal Proceedings of the National Academy of Sciences, Thanavala and colleagues report on the first human, or clinical, trial for a plant-derived HBV vaccine. HBV is transmitted by blood or sexual fluids.
For the clinical trial, the researchers genetically modified potatoes to carry the gene for the hepatitis B surface antigen. An antigen is a foreign substance, usually a protein, that, when absorbed by the body, triggers an immune response.
In the trial of 42 participants previously inoculated with the traditional hepatitis B vaccine, about 60 percent showed signs of boosted immunity after eating bite-size pieces of raw genetically modified spuds.
Charles Arntzen, a pioneer in the development of plant-derived vaccines and a co-author of the paper, said he was pleased at the success of the trial.
"We had seen very good responses in mice, so anticipated that we might get good responses in humans. But mice and humans are very different, so we were delighted," said Arntzen, who works with the Biodesign Institute at Arizona State University in Tempe.
The results were particularly impressive, Thanavala said, since the vaccine lacked an adjuvant. An adjuvant is a substance added to a vaccine to improve the immune response.
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